Apparatus and method for vacuum freeze drying substances in a tunnel dryer having sealing locks



July 6, 1965 GEORG-WILHELM OETJEN ETAL APPARATUS AND METHOD FOR VACUUM FREEZE DRYING SUBSTANCES IN A TUNNEL DRYER HAVING SEALING LOCKS Filed July 22, 1960 v 6240 III-235V a 2 Sheets-Sheet 1 lawezai'oau: wag-1022302823 Oefin, liwiiaez'nz Neuazauzam Jamil M023, Wz'lkeim Henge,

by MW 6. W Jawrne y 1965 GEORG-WILHELM OETJEN ETAL 3,192,645

APPARATUS AND METHOD FOR VACUUM FREEZE DRYING SUBSTANCES IN A TUNNEL DRYER HAVING SEALING LOCKS Flled July 22, 1960 2 Sheets-Sheet 2 I W l l a0 /7 80 a0 /7 a0 a /7 a0 a,- o a;

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fig 96% 6'. Jlitavney United States Patent Office 3,192,645 AFPARATUS AND METHDD FUR VACUUM FREEZE DRYENG SUBSTANCES IN A TUN- NEL DRYER HAVKNG SEALENG LGQKS Georg-Wilhelm (tetjen, (Ioiogne-ltiarienbnrg, Wiiheim Nerge, Rodenidrchen, Karlheinz Nenmann, Uoiogne- Eayental, and Iustus Mail, Meschenich, Germany, assiguors, by mesne assignments, to Leyhoid-Aniagen Holding, A.G., Zug, Switzerland Filed .lnly 22, 196i), Ser. No. 44,632 Claims priority, application Germany, Oct. 7, 1959,

L 34,426 29 Claims. (Ci. 34--92) The present invention relates to a freeze drying method and installation and, more particularly, relates to a freeze drier installation in which the goods to be dried are introduced into an inlet air lock and are moved through a vacuum space, while being exposed to heat, whereafter the goods are removed through an outlet air lock.

As a consideration of the technical literature will show, the freeze drying industry has long appreciated the economic advantages realizable from a large scale continuous freeze drying operation. However, it was not possible, heretofore, to provide a practical installation to carry out such large scale operation. Thus, While there exists a number of continuous freeze drying systems, none has been found suitable for the operation of a really large industrial installation, for reasons which will be set forth below.

In one of such known systems, the goods to be dried are introduced through an inlet air lock and are placed onto a continuously driven moving belt, so as to form a thin layer of the goods. The goods are then moved through a vacuum chamber in which a uniform pressure is maintained, whereafter the goods are removed through an outlet air lock. If such an arrangement were used in a large industrial installation, and if the installation were designed for a daily capacity of 20 tons, this would require a transport belt having a surface area of about 400 m? and this, in turn, would necessitate such a huge apparatus as to render it impractical, because the drying chamber would have to be exceptionally large, to say nothing of the difficult problems arising in a system in which such a large endless belt has to be operated in a vacuum.

In another continuous freeze drier installation of known type, the receptacles for the goods to be dried are moved through the vacuum chamber along a zigzag path past the heating plates and, in order to accomplish this, a complicated transport mechanism, including appropriate direction changing devices, must be provided. Thus, if an installation of this type were designated for daily capacity of 20 tons, the large number of receptacles which would have to be moved would give rise to virtually insurmountable mechanical difficulties.

It is, therefore, an object of the present invention to provide a freeze drying method and installation which is capable of being operated on a very large scale, but which overcomes the disadvantages of the heretofore known systems.

It is another object of the present invention to provide a freeze drier installation which is of simple construction, so that large quantities of goods may be dried without mechanical or other technical difficulties.

The objects of the present invention also include the provision of a freeze drier installation which is capable of handling large quantities of goods and which will give long periods of trouble-free service.

With the above objects in view, the present invention resides mainly in a freeze drier installation which comprises means forming a vacuum space, a material feeding lock and a material discharging lock communicating with the vacuum space, means allowing the movement 'of goods to be dried from the material feeding lock through the vacuum space to the material discharging lock, and heating means arranged in the vacuum space and having substantially parallel heating surfaces lying in planes substantially parallel to the direction of movement of the goods, these goods passing between the heating surfaces. According to a preferred embodiment of the present invention, the vacuum space is divided into a series of vacuum chambers, the first of which is in communication with the material feeding lock and the last in communication with the material discharging lock, and there are moving means for moving the goods to be dried through the series of vacuum chambers.

Additional objects and advantages of the present invention will become apparent upon consideration of the following description when taken in conjunction with the accompanying drawings, in which:

FIGURE 1 is a schematic longitudinal sectional view of a freeze drier installation according to the present invention;

FIGURE 2 is a transverse sectional view of the installation shown in FIGURE 1;

FIGURE 3 is a perspective view of a carrier for moving the goods to be dried through the vacuum chambers; and

FIGURE 4 is a fragmentary plan view, showing the juncture of adjacent vacuum chambers.

Referring in detil to the drawings and, particularly, FIGURES 1 and 2 thereof, there is shown a generally tubular freeze drier installation having a material feeding or inlet air lock chamber 1 communicating with a vacuum chamber 2, this chamber being the first of a series of vacuum chambers 2, 3, 4 and 5 which, together, form the vacuum space of the installation. The last chamber 5 communicates with a material discharging or outlet air lock chamber 6, said outlet air lock chamber, as well as the inlet air lock chamber 1, being provided with a cover 7 which may be opened so as to allow the introduction and removal of the goods to be dried.

The inlet air lock chamber 1 is placed in communication with a condenser 9 by way of a connecting conduit 8, the conduits for supplying the condenser 9 with low temperature heat exchange liquid being shown at 10. The casing of the condenser 9 is also in communication with vacuum pump 11 so that the interior of the chamber 1 may be evacuated.

Within the vacuum chambers 2, 3, 4 and 5, there are arranged fixedly mounted heating elements 12 having heating surfaces lying in substantially parallel planes. The heating elements 12 can be any well known type such as, for example, steam, electrical, dielectric, etc. In the embodiment illustrated, these planes are horizontal and form box-like spaces between each other. Suitable conveyor transport means are provided to allow movement of receptacles 14 containing the goods to be dried between the heating surfaces, i.e., the goods travel ina direction parallel to the planes of the heating surfaces and pass between said surfaces.

As shown in FIGURE 3, the conveyor transport means are in the form of a carrier 13 comprising a channelshaped member 17 having at each of its ends a pair of rollers 15. A U-shaped central member 18 is attached to the channel-shaped member 17, said central member 13 being provided with transverse cantilever support arms 19 extending laterally into the substantially parallel spaces formed between adjacent heating surfaces. As illustrated in FIGURE 3, the transverse arms are adapted tosupport the bent-overcurved ends 243 of the receptacles '14 which in turn support the material to be processed in substantially parallel planes. Thus the bottom surfaces of trays 14 are Patented July 6, 1965 3 exposed to allow direct radiant and convection heating by the heaters 12.

The vacuum chambers 2, 3 and 5 communicate with condensers 21, 22 and 23 by way of conduits 24, 25 and 26, respectively, as well as with vacuum pumps 27, 28 and 29, respectively, to evacuate the particular chambers with which they are in communication. The heating elements in chambers 3 and 4 are similarly arranged. It will be noted, however, that there is no condenser or vacuum pump in communication with the chamber 4. This chamber is evacuated by the adjacent condensers 22, 23 and pumps 28, 29 through the partial seals created by the doors 32. A further vacuum pump 30 is in communication with the outlet air lock chamber 6, which chamber, however, is not provided with a condenser.

The carriers 13 are mounted for movement along an overhead guide rail .16, shown as an I beam, which is supported for movement with the pistons 16a of hydraulic lift mechanisms 16b and the individual carriers 13 are moved through the installation by a chain 31. The electromechanical drive system for the carriers is of conventional construction; it may, for instance, include a sprocket wheel 31a which engages the conveyor chain 31, and an intermittently actuated drive motor 31b. It is to be understood that the train of carriers .13 is such that, as each carrier enters the outlet air lock chamber 6, it can be re moved from the chain 31 and, thus, be taken out of the installation. Conversely, a carrier supporting receptacles 14 with fresh material can be introduced into the inlet air lock chamber 1 and can be hooked on to the chain 31.

As shown in FIGURES 2 and 4, the partitions between the individual vacuum chambers are provided with doorlike closure elements 32 which, in closed position, serve to shut off the chambers from each other substantially fluid-tightly. The closure elements 32 can be actuated by abutments 33 mounted on the carriers 13, said abutments causing the closure elements to open whenever a carrier moves from one chamber to the next, or by suitable remote controlled devices (not shown). The actual shape of each door 32 may best be seen from FIGURE 2 in which, for the sake of clarity, the outline of but one of the two doors is shown in dashed lines, it being understood that the other door is in mirror-image symmetry therewith. The pivot axis of the door is indicated at 32a. It will be appreciated that the edges of the cooperating doors,

. which may be made of elastic material, will overlap each other, thereby producing the substantial if not absolute fluid-tightness which is all that is required since, in practice, the pressure difference in adjacent chambers will be very small. Since there is substantially no movement of the conveyor chain while the doors are closed, there will be no problem insofar as interengagement between the doors and chain is concerned. Also, it will be seen from FIG- URE 2 that since the doors need to open only wide enough to allow the passage of the receptacles 14, the upper edges of the doors will clear the wall of the chamber by a sufficient margin, particularly since design considerations may easily allow a modification of the doors so as to permit the same to open sufiiciently to produce the desired result.

Operation The operation of the freeze drier installation embodiment of FIGURE 1 takes place in the following manner.

The goods to be dried are charged into the receptacles while the same are still outside of the actual drier, after which the containers are placed onto one of the carriers 13 and into the inlet air lock chamber 1. Thereafter, the goods are frozen in this chamber by rapid evaporation of water from the surfaces of the goods produced by the water vapor condenser 9. Alternatively, the goods may be frozen prior to charging into the installation. The carriers 13 are then advanced intermittently through the series of vacuum chambers towards the outlet air lock chamber 6. This movement is timed such that whenever the vessels 14 are at rest, they will be in a position wherein the goods are maintained in the optimum effective zone of the heating elements 12, i.e., the vessels 14 will be in the boxlike space formed between two parallel heating surfaces whenever the carrier is at rest. Additionally the hydraulic lift mechanisms 16b permit vertical adjustment of the conveyor carriers 13. In this way the receptacle trays 14 can during rest periods be lowered into a position wherein they are in direct contact with a heating surface. Thus the heating surfaces will be in direct contact with the receptacles 14 as support surfaces therefor.

Whenever the carriers 13 are advanced from one chambcr to the next, the closure elements 32 are engaged by abutments 33, so as to open and to allow the entrance of a carrier. After a particular carrier has entered the new chamber, the closure elements 32 will close, thereby effectively fluid-tightly sealing the chamber, thereby maintaining different pressures in the individual vacuum chambers. Due to water vapor, it is also possible to maintain in each chamber a different partial pressure by controlling the surface temperature of the individual condensers 9, 21, 22 and 23. As is well known, the interrelation between the surface temperature of the condenser and the partial pressure of the water vapor may be determined by appropriate steam tables.

It will be appreciated that, since each of the individual vacuum chambers can for certain periods be sealed substantially fluid-tightly from each other, the goods can be dried to any desired degree. With the conduits 24, 25 and 26 closed by valves 24a, 25a, and 26a, as well as the closure elements 32 being closed, the entire installation forms a closed system. The pressure increase during a predetermined period can then be determined, from which the degree of dryness of the goods can be calculated. Thus, the progress of the drying operation, as the goods move from chamber to chamber, can be kept under constant surveillance. Finally, the goods reach the outlet air lock chamber 6 in which a high vacuum is maintained by the vacuum pump 30. The goods may then be removed from the installation. If desired, the receptacles may first be hermetically sealed so as to prevent the entry of atmospheric air. The precise manner in which this is done does not form any part of the present invention; in practice, however, the sealing may be accomplished, for instance, by automatic plunger-type means which engage cover-like flaps overlying the receptacles so as to close the same.

Alternatively, the goods may be subjected in a step-wise manner to the conditions prevailing in the vacuum chambers by moving the goods intermittently and periodically opening and closing the closure elements 32. The intermittent movement itself may be carried out at a constant rate, in the sense that the goods will be caused to move through the same number of chambers per unit time. This may be accomplished simply by so spacing and dimensioning the carriers that each single carrier, or group of carriers, will remain within each chamber for a certain period of time, during which the closure elements are closed.

It will be understood that the above description of the present invention is susceptible to various modifications, changes and adaptations, and the same are intended to be comprehended within the meaning and range of equivalents of the appended claims. For example, it is possible to provide an arrangement wherein, instead of moving the goods past the heating surfaces, the goods aremain tained at rest and the heating elements are moved, the essential feature being to produce relative movement between the goods and the heating elements.

It will also be appreciated that, instead of the flap-like closure elements, different types of closure means may be provided which are capable of sealing successive chambers tightly enough to allow different low pressures to prevail in adjacent chambers without, however, it being necessary that the seal between adjacent chambers be sufliciently tight to seal the various high vacuum chamhers against atmospheric pressure. Thus, the sealing means may be of relatively simple construction.

Also, it will be understood that the vacuum space may be compartmented into any suitable number of individual chambers, such as five, twenty or a hundred, or more. Experience has shown, however, that ton to twenty individual vacuum chambers are generally adequate, although a greater or lesser number may, in practice, be used.

Furthermore, since the individual chambers and the heating elements therewithin are of similar construction, it is possible to treat each chamber as a unit and to build up an installation by using the desired number of units. The size of the installation can thus readily be increased or decreased. Also, if any one unit needs servicing or otherwise becomes defective, it is quite simple to exchange it for another; if there is a conveyor chain such as is shown in connection with some of the embodiments, such chain can readily be disconnected at the appropriate points. Thus, the breakdown of any one unit will not disable the entire installation. To this end, it has been found particularly practical to provide a rail track system on which the individual units are movably mounted.

In order to allow the pressure and temperature conditions as well as the partial water vapor pressure in each vacuum chamber to be regulated independently of the other uints, it has been found expedient to provide individual controls for the heating means, condenser and vacuum pump associated with each chamber. Here, it should be noted that, instead of providing surface condensers, water vapor spray suction devices or gas ballast pumps may be used.

We claim:

1. A freeze drying method for use in a freeze drying installation having an evacuable feeding lock, an evacuable discharge lock, an evacuable drying chamber connected between the feeding and discharge locks and separated therefrom by door mechanisms adapted to maintain a pressure differential and to allow passage of a material to be dried, a refrigerated condenser connected for gas communication with the evacuable feeding lock, heating means positioned in said drying chamber and adapted to apply sublimation inducing heat to a material being dried, and water vapor removal apparatus connected to said drying chamber and adapted to remove Water vapor produced by said sublimation, which method comprises the following steps: positioning the material to be dried into the feeding lock, evacuating the feeding lock, producing within the feeding lock rapid surface evaporation of the material to cause freezing thereof, transporting the frozen material into the evacuated drying chamber, freeze drying the material within the drying chamber, transporting the dried material into the evacuated discharge lock, and removing the dried material from the discharge lock.

2. A freeze drying method for use in a freeze drying installation having an evacuable feeding lock, an evacuable discharge lock, an evacuable drying chamber connected between the feeding and discharge locks and separated therefrom by door mechanisms adapted to maintain a pressure differential and to allow passage of a material to be dried, heating means positioned in said drying chamber and adapted to apply sublimation inducing heat to a material being dried, and water vapor removal apparatus connected to said drying chamber and adapted to remove water vapor produced by said sublimation which method comprises the following steps: positioning the material to be dried into the feeding lock, evacuating the feeding lock, transporting the frozen material into the evacuated drying chamber, freeze drying the material within the drying chamber, transporting the dried material into the evacuated discharge lock, enclosing the dried material in hermetically sealed enclosures, and removing the dried material from the discharge lock.

3. A freeze drying method for use in a freeze drying installation having an evacuable feeding lock, an evacuable discharge lock, an evacuable drying chamber connected between the feeding and discharge locks and separated therefrom by door mechanisms adapted to maintain a pressure differential and to allow passage of a material to be dried, heating means positioned in said drying chamber and adapted to apply sublimation inducing heat to a material being dried, and water vapor removal apparatus connected to said drying chamber and adapted to remove Water vapor produced by said sublimation, which n ethod comprises the following steps: loading a material to be dried into material trays, positioning the material trays in the feeding lock, evacuating the material feeding lock, transporting the material trays into the drying chamber while providing a mechanical clearance between the heating means and the material trays, freeze drying the material within the drying chamber while maintaining a direct contact between the material trays and the heating means, transporting the trays filled with dried material into the evacuated discharge lock, and removing the dried material from the material discharge lock.

' 4. A freeze drying method for use in a freeze drying installation having an evacuable feeding lock, an evacuable discharge lock, an evacuable drying chamber connected between the feeding and discharge locks and separted therefrom by door mechanism adapted to maintain a pressure dilferential and to allow passage of a frozen material to be dried, heating means positioned in said drying chamber and adapted to apply sublimation inducing heat to the material being dried, and at least two refrigerated condensers each connected through valves to said drying chamber and adapted to remove Water vapor produced by said sublimation, which method comprises the following steps: positioning the frozen material in the feeding lock, evacuating the material feeding lock, transporting the material into the evacuated drying chamber, applying heat to the material in the evacuated drying chamber to produce sublimation of the frozen moisture contained in the material, condensing the water vapor formed by said sublimation with a first refrigerated condenser, isolating the first refrigerated condenser from the evacuated drying chamber, connecting a second refrigerated condenser to the evacuated drying chamber for removal of an additional quantity of water vapor formed by said sublimation, transporting the material from the discharge lock.

5. A freeze-drying apparatus comprising a vacuum chamber, vacuum pumping means adapted to provide evacuation of said vacuum chamber, said vacuum chamber having a movable wall portion adapted to provide an entrance to said vacuum chamber, heating means arranged in said vacuum chamber and having a plurality of substantially parallel-oriented heating surfaces, said substantially parallel heating surfaces being spaced apart to form a plurality of substantially parallel spaces therebetween, conveyor means adapted to support a frozen substance to be dried in said vacuum chamber, said conveyor means including support means adapted to support the frozen substance in a plurality of substantially parallel planes, and guide means extending into said vacuum chamber and adapted to guide movement of said conveyor means within said vacuum chamber wherein the frozen substance supported in substantially parallel planes partially fills the spaces formed by said plurality of substantially parallel heating surfaces so as to allow the application of sublimation-producing heat to the,

frozen substance.

6. The apparatus according to claim 5 wherein said support means includes a plurality of removable substance containable trays which form substantially parallel planes.

7. The apparatus according to claim 6 wherein said substance containable trays are supported so as to expose the bottom surfaces of said substance containable trays thereby allowing the bottoms of said substance containable trays to be directly heated by radiation and convection from said heating means.

8. The apparatus according to claim wherein said guide means includes a rail extending into said vacuum chamber, said conveyor means includes a center member mounted on said rail for movement therealong, and said support means comprises transverse arms arranged on said central member and adapted to extend laterally into the spaces formed between said plurality of substantially parallel heating surfaces.

9. The apparatus according to claim 8 wherein said support means further includes a plurality of removable substance containable trays which are supported by said transverse arms so as to form substantially parallel planes.

10. The apparatus according to claim 9 wherein said substance containable trays are supported so as to expose the bottom Surfaces of said substance containable trays thereby allowing the bottoms of said substance containable trays to be directly heated by radiation and convection from said heating means.

11. The apparatus according to claim 5 wherein said heating means are substantially horizontal and are mounted from opposite sides of said vacuum chamber extending inwardly thereof, said heating means mounted rom one side of said vacuum chamber being spaced from said heating means mounted from the opposite side of said vacuum chamber so as to form a transverse passageway therebetween, said guide means comprises a rail extending into said vacuum chamber, said conveyor means includes a central member mounted on said rail for movement therealong, said central member being adapted for movement through the transverse passageway formed between said heating means mounted from opposite sides of said vacuum chamber, and said support means comprises a plurality of transverse cantilever arms arranged on said central member so as to extend laterally into the spaces formed between said parallel-oriented heating surfaces.

12. The apparatus according to claim 11 wherein said support means further includes a plurality of removable substance containable trays which are supported by said transverse cantilever arms and form substantially parallel planes.

13. The apparatus according to claim 12. wherein said substance containable trays are supported by said transverse arms so as to expose the bottom surfaces of said substance containable trays thereby allowing the bottoms of said substance containable trays to be directly heated by radiation and convection from said heating means.

14. The apparatus according to claim 5 including adjustment means for producing movement of said conveyor means in transverse directions to said paralleloriented heating means so as to permit in one position of said adjustment means the attainment of a mechanical clearance between said heating surfaces and said conveyor means during movement thereof along said guide means and to permit in a second position of said adjustment means the attainment of direct contact between said heating surfaces and said conveyor means.

15. The apparatus according to claim 14 wherein said support means includes a plurality of removable substance containable trays which form substantially parallel planes.

16. The apparatus according to claim 15 wherein said substance containable trays are supported so as to completely expose the bottom surfaces of said substance containable trays thereby allowing a direct contact between said heating surfaces and said substance containable tray bottoms in the second position of said adjustment means.

17. The apparatus according to claim 14 wherein said heating means are substantially horizontal and are mounted from opposite sides of said vacuum chamber extending inwardly thereof, said heating means mounted from one side of said vacuum chamber being spaced from said heating means mounted from the opposite side of said vacuum chamber so as to form a transverse passageway therebetween, said guide means comprises a rail extending into said vacuum chamber, said conveyor means includes a central member mounted on said rail for movement therealong, said central member being adapted for movement through the transverse passageway formed between said heating means mounted from opposite sides of said vacuum chamber, and said support means comprises a plurality of transverse arms arranged on said central member so as to extend laterally into the spaces formed between said parallel-oriented heating surfaces.

18. The apparatus according to claim 17 wherein said support means further includes a plurality of removable substance containable trays which are supported by said transverse arms and form substantially parallel planes.

19. The apparatus according to claim 18 wherein said substance containable trays are supported by said transverse arms so as to completely expose the bottom surfaces of said substance containable trays thereby allowing a direct contact between said heating surfaces and said substance containable tray bottoms in the second position of said adjustment means.

20. A freeze-drying apparatus comprising a vacuum chamber, a frozen material-feeding lock adapted to be evacuated and connected for direct communication with said vacuum chamber, a material-discharge lock adapted to be evacuated and connected for direct communication with said vacuum chamber, a movable feeding wall portion positioned between said material-feeding lock and said vacuum chamber and adapted to maintain a pressure differential therebetween, a movable discharge wall portion positioned between said material-discharge lock and said vacuum chamber and adapted to maintain a pressure differential therebetween, a movable entrance door adapted to allow entrance into said material-feeding lock of a material to be freeze-dried, a movable exit door adapted to allow removal from said material-discharge lock of the freeze-dried material, vacuum pumping means connected to each of said material-feeding and material-discharge locks for evacuation thereof, conveyor means adapted to transport the material from said materialfeeding lock through said vacuum chamber and into said material-discharge look, at least two refrigerated water vapor condensers connected for gas communication with said vacuum chamber and adapted to remove water vapor sublimating from the material, valve means for providing gas isolation between said vacuum chamber and said refrigerated water vapor condensers, and heating means positioned in said vacuum chamber and adapted to provide sublimation inducing heat to the frozen material.

21. The apparatus according to claim 20 wherein said vacuum chamber comprises a plurality of separate compartments and including movable walls dividing said compartments and adapted to maintain a pressure differential between said compartments and to allow passage of said conveyor means.

22. The apparatus according to claim 21 wherein said separate compartments are modular units of similar construction.

23. The apparatus according to claim 21 wherein said heating means comprises a plurality of substantially paraL lel-oriented heating surfaces, said substantially parallel heating surfaces being spaced apart to form a plurality of substantially parallel spaces therebetween, said conveyor means including support means adapted to support the frozen material in a plurality of substantially parallel planes, and guide means positioned in said vacuum chamber and adapted to guide said conveyor means within said vacuum chamber wherein the frozen material supported parallel planes partially fills the spaces formed by said plurality of substantially parallel heating surf-aces.

24. The apparatus according to claim 23 wherein said guide means includes a rail extending into said vacuum chamber, said conveyor means includes a central member mounted on said rail for movement therealong, and said support means comprises transverse arms arranged on said central member and adapted to extend laterally into the spaces formed between said plurality of substantially parallel heating surfaces.

25. The apparatus according to claim 23 wherein said heating means are substantially horizontal and are mounted from opposite sides of said vacuum chamber extending inwardly thereof, said heating means mounted from one side of said vacuum chamber being spaced from said heating means mounted from the opposite side of said vacuum chamber so as to form a transverse passageway therebetween, said guide means comprises a rail extending into said vacuum chamber, said conveyor means includes a central member mounted on said rail for movement therealong through the transverse passageway formed between said heating means mounted from opposite sides of said vacuum chamber, and said support means comprises a plurality of transverse arms arranged on said central member so as to extend laterally into the spaces formed by said parallel-oriented heating surfaces.

26. The apparatus according to claim 23 including adjustment means for producing movement of said conveyor means in transverse directions to said parallel-oriented heating means so as to permit in one position of said adjustment means the attainment of a mechanical clearance between said heating surfaces and said conveyor means during movement thereof along said guide means and to permit in a second position of said adjustment means the attainment of direct contact between said heat into said vacuum chamber, said conveyor means includes a central member mounted on said rail for movement therealong, said central member being adapted for movement through the transverse passageway formed between said heating means mounted from opposite sides of said vacuum chamber, and said support means comprises a plurality of transverse arms arranged on said central member so as to extend laterally into the spaces formed between said parallel-oriented heating surfaces.

28. The apparatus according to claim 26 wherein said support means includes a lurality of removable substance containable trays which are supported in substantially parallel planes.

29. The apparatus according to claim 28 wherein said substance containable trays are supported as to expose the bottom surfaces of said substance containable trays thereby allowing a direct contact between said heating sur faces and said substance cont-ainable tray bottoms in the second position of said adjustment means.

References Cited by the Examiner UNITED STATES PATENTS 414,204 11/89 Foss 342l6 X 620,139 2/ 99 Hysore 342l6 X 655,710 8/00 Hirt 3455 717,265 12/02 Passburg 3415 X 749,627 1/04 Passburg 3415 2,362,117 11/44 David 3492 2,370,422 2/45 Reed 34193 2,384,500 9/45 Stoll 3492 2,419,875 4/47 Birdseye. 2,523,552 '9/50 Birdseye 345 X 2,643,761 6/53 Wagner et a1 l98177 2,872,057 2/59 Wagner et a1 198-477 2,989,026 6/61 Gardner et al 11849 FOREIGN PATENTS 1,119,453 6/56 France.

NORMAN YUDOFF, Primary Examiner.

CHARLES OCONNELL, BENJAMIN BENDETT,

' Examiners. 

1. A FREEZE DRYING METHOD FOR USE IN A FREEZE DRYING INSTALLATION HAVING AN EVACUABLE FEEDING LOCK, AN EVACUABLE DISCHARGE LOCK, AN EVACUABLE DRYING CHAMBER CONNECTED BETWEEN THE FEEDING AND DISCHARGE LOCKS AND SEPARATED THEREFROM BY DOOR MECHANISMS ADAPTED TO MAINTAIN A PRESSURE DIFFERENTIAL AND TO ALLOW PASSAGE OF A MATERIAL TO BE DRIED, A REFRIGERATED CONDENSER CONNECTED FOR GAS COMMUNICATION WITH THE EVACUABLE FEEDING LOCK, HEATING MEANS POSITIONED IN SAID DRYING CHAMBER AND ADAPTED TO APPLY SUBLIMATION INDUCING HEAT TO A MATERIAL BEING DRIED, AND WATER VAPOR REMOVAL APPARATUS CONNECTED TO SAID DRYING CHAMBER AND ADAPTED TO REMOVE WATER VAPOR PRODUCED BY SAID SUBLIMATION, WHICH METHOD COMPRISES THE FOLLOWING STEPS; POSITIONING THE MATERIAL TO BE DRIED INTO THE FEEDING LOCK, EVACUATING THE FEEDING LOCK, PRODUCING WITHIN THE FEEDING LOCK RAPID SURFACE EVAPORATION OF THE MATERIAL TO CAUSE FREEZING THEREOF, TRANSPORTING THE FROZEN MATERIAL INTO THE EVACUATED DRYING CHAMBER, FREEZE DRYING THE MATERIAL WITHIN THE DRYING CHAMBER, TRANSPORTING THE DRIED MATERIAL INTO THE EVACUATED DISCHARGE LOCK, AND REMOVING THE DRIED MATERIAL FROM THE DISCHARGE LOCK. 